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​Cihat Şen, ​Nicola Volpe

Cecilia Villalain, Daniel Rolnik, M. Mar Gil

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Murat Yayla

Statistics Editor
Resul Arısoy

Multicentric multiple pregnancy study IV: mortality in twins – spontaneuos versus artificial reproductive techniques

Murat Yayla, Rahime Nida Ergin, Yeşim Baytur

Article info

Multicentric multiple pregnancy study IV: mortality in twins – spontaneuos versus artificial reproductive techniques. Perinatal Journal 2011;19(1):1-5

Author(s) Information

Murat Yayla1,
Rahime Nida Ergin1,
Yeşim Baytur2

  1. International Hospital Kadın Doğum Kliniği- İstanbul TR
  2. Celal Bayar Üniversitesi Tıp Fakültesi Kadın Hastalıkları ve Doğum Anabilim Dalı- Manisa TR
Publication History
Conflicts of Interest

No conflicts declared.

Both spontaneous and ART twin pregnancies have maternal and fetal risks. In this multi-centered cross-sectional study we aimed to determine prognostic differences between spontaneous and ART twin pregnancies in some centers of our country.
Demographic data of women delivered between the period of 2003 and 2004, including mean maternal age, parity, fetal and perinatal mortality, gestational week at delivery, mode of delivery and maternal morbidity, fetal or newborn’s weight and sex were determined from the questionnaire forms and data obtained from 10 obstetrics centers from different parts of Turkey, including university and Health Ministry training hospitals.
The number of twins among the births in ten centers participated in the study was 818. The percentage of spontaneous twins was 24% whereas in 76% ART was applied. There was no difference in the mean age of mothers between the groups. Mean birth week of spontaneous twins was 35.03±2.58 weeks and mean birth week of ART twins was 34.31±3.51 weeks. The ratio of caeserean section in ART and spontaneous twins were 78.6% and 68.8% respectively. While late second trimester mortality was high in ART group and third trimester mortality was high in spontaneous group, perinatal mortaliy was similar between two groups.
In our study there was no significant difference in the perinatal mortaliy between ART and spontaneous twins.

Twin pregnancy, mortality, artificial reproductive techniques, spontaneous

Progress in the artificial reproductive techniques (ART) is the cause of the increase of the ratio of multiple pregnancies at the present. The success of centers using induction of ovulation, in vitro fertilization ( IVF) or intracytoplasmic sperm injection (ICSI) is measured by the ratio of pregnancy, meanwhile, the real measure, the healthy fetus at term (favorably singleton) is sometimes ignored. Because of the reduced pregnancy rates by the conservative approaches in the favor of Singleton pregnancies and the psychological stress brought by failed pregnancy after a long and expensive treatment processes and to prevent the decrease in the success of the Assisted Reproductive Technique (ART) centers, implementation of aggressive therapies which may result multiple pregnancies are preferred. However, both spontaneous and ART multiple pregnancies are accompanied by maternal and fetal risks.[1-4] Although the increased ratio of multiple pregnancies in our country has been mentioned in many scientific meetings, no comprehensive national study has been planned to determine the factors related to the increase of multiple pregnancies and maternal/fetal mortality and morbidity related to these multiple pregnancies. The comprehensive multi-centered studies related on this subject have been published by the present study group.[5,6] The aim of this cross-sectional multi-center study was to reveal the mortality ratios in the spontaneous and ART twins in various Obstetrics and Gynecology clinics in our country.
Demographic data of women delivered between the period of 2003 and 2004, including mean maternal age, parity, fetal and perinatal mortality, gestational week at delivery, mode of delivery and maternal morbidity, fetal or newborn’s weight and sex were determined from the questionnaire forms and data obtained from 10 obstetrics centers from different parts of Turkey, including university and Health Ministry training hospitals. Some unreported data in the survey were re-questioned and the missing ones were completed. Ovulation induction, ICSI and IVF pregnancies have been accepted as assisted reproductive techniques. The term “stillbirth” has been defined for the death of the fetus, who (or any of his twins) is at least 400 grams of weight or who completed 20 th gestational week, before birth or no respiration after birth or no heart beat. The term “early neonatal death” has been defined for neonatal deaths within the first 7 days after birth. The data of spontaneous and ART twin pregnancies were compared using statistical tests of chi-square, Fisher's exact and Student's t-test. SPSS for Windows version 14.0 (SPSS Inc, Chicago, IL, ABD) was used for statistical analyses. The value of p <0.05 was accepted as significant.
The total number of births was 43.258 between 2003 and 2004 in ten centers which participated in the study. The total numbers of twins were 818 (18.9/1000) and the total numbers of triplets was 42 (0.97/1000). The data of type of pregnancy was available in 265 twins and 24.15% of them were spontaneous and in 75.85% of them ART was applied. The demographics of both spontaneous and ART twins are given in the table 1. There was no significant difference in the mean maternal age. The only significant difference was higher number of previous gestations in the spontaneous twin pregnancies as expected. Mean birth weeks were 34.31 ± 3.51weeks in ART twins and 35.03 ± 2.58 weeks in spontaneous twins. The perinatal mortality ratio in the twin pregnancies was 106.9/1000 and the mortality ratio and survival ratios according to the type of pregnancy are given in the Table 2. The chance of being alive of both fetuses was 10% higher in ART twins though not statistically significant. Concerning the type of delivery, the ratio of death of at least one fetus was 7.7% and the ratio of live birth of both fetuses was 92.3% in caesarean section. These ratios were 42.1% and 57.9% in vaginal deliveries. The mortality ratios in births with caesarean section and vaginal deliveries according to the type of pregnancy are given in the Table 3. When the spontaneous and ART twins were compared according to the mean weights of live and dead fetuses, mean weights of ART twins were lesser in all groups. But this difference was found to be statistically significant only in the group where both fetuses were dead (Table 4). Survival ratios were lower in fetuses with weight of ≤1500 grams in both spontaneous and ART pregnancies (Table 5). When the spontaneous and ART twins were grouped as both living or both deceased or one deceased, mean week of birth was lower in all ART groups. Fetal loss ratio was higher in the late second trimester in ART twins whereas fetal loss ratio was higher in the third trimester in spontaneous twins. Therefore, mean gestational week was significantly lower in the ART twins who both deceased compared to the corresponding spontaneous twin group (Table 6). Live birth ratios were lower in both genders of spontaneous twins compared to ART twins. Survival rates and mortality ratios were similar in both genders of spontaneous pregnancies. However, mortality ratio of female gender was aproximately half of the mortality ratio of male gender in ART pregnancies (p >0.05) (Table 7). Maternal morbidity factors were more in the twin pregnancies with perinatal mortality. However, there was no significant difference between spontaneous and ART pregnancies.
Chorionicity is an important factor for the complications in the twin pregnancies. As, fetal risks like fetal loss, preterm birth or IUGR is higher in the monochorionic pregnancies compared to dichorionic ones.[7] In a study with large numbers of twins reported from our country the ratio of dichorionic pregnancies was 85% and the mortality ratio of these was 6%. The ratio of monochorionic pregnancies was 15% but the mortality ratio of these was 14%.[8] It was not possible to determine the distribution of chorionicity in our study due to design of study and some missing data in the records. Compared to the singleton pregnancies, stillbirths are seen twice more in ART twin pregnancies.[9] However, perinatal prognoses of ART twins are indifference with spontaneous twins and even a little better, though ART twins are more preterm and have lower birth weights.[10-12] It has been suggested that maternal complications, birth weeks and birth weights are not different in such pregnancies.[13] This is explained by that monochorionic twins are encountered rare in ART twins (32% versus 7%) and that the complications occur rarely.[14]. However, in a study from our country comparing 274 ART and 348 spontaneous twins the findings were in conflict. In this twin study preterm birth before 37 weeks and birth weight of ≤2,500 grams were found 20% higher. Preterm birth before 32 weeks and birth weight of ≤1,500 grams were found 40% higher. Perinatal mortality was thrice higher and perinatal morbidity was twice higher and the general prognosis was worse.[15] These were not confirmed by the study of Güney et al only increased EMR and 120 grams lesser mean birth weights were reported in the ART twin pregnancies.[16] The differences in these studies may probably be due to morbidity criteria of the studies and the differences in the monochorionic pregnancy ratios. In a study comparing 112 spontaneous twins and 56 ART twins, Nassar et al reported the ratio of caesarean section as 58% in spontaneous twins and 77% in ART twins. They also reported that preterm birth ratios and respiratory complications related to this were higher in ART group.[17] Vasario et al found no significant difference in neonatal outcomes between 139 spontaneous twins and 84 IVF twins and they found non-significant higher rate of caesarean section in ART group.[18] Similarly, Luke et al found no difference in terms of complications when compared 2,143 spontaneous and 424 ART twin pregnancies.[19] In our study we found no significant effect of ART considering the mortality and survival ratios. We found higher rates of caesarean section and earlier birth weeks and, as a consequence, lesser birth weights in ART twin pregnancies compared to spontaneous twin pregnancies. Though earlier birth weeks in ART twin pregnancies is not statistically significant, this may be due to preference of caesarean section more in ART twin pregnancies. In spite of the fact that no difference was found in the mortality rates between spontaneous and ART twins in our study, it should be kept in mind that multiple pregnancies increase the maternal and fetal risks compared to singleton pregnancies and that implantation of more than three embryos does not increase the chance of live birth instead increase the complications.[1-4,20] In addition, it has been suggested that 4% decrease in perinatal mortality will occur if more than one fetus is prevented in ART.[21]
In our study there was no significant statistical difference in the perinatal mortality between ART and spontaneous twins though the risk was higher in spontaneous twins and male fetuses. However, it is to kept in mind that high numbers of twins due to ART pregnancies will increase the complications compared to the singleton pregnancies.
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Table 1.
Demographics of spontaneous and ART twins.
Table 2.
Mortality in spontaneous and ART twins.
Table 3.
Types of pregnancy and delivery in spontaneous and ART twins.
Table 4.
Birth weights of spontaneous and ART twins.
Tablo 5.
Mortality in spontaneous and ART twins according to birth weights.
Table 6.
Mortality and gestational weeks in spontaneous and ART twins.
Table 7.
Mortality in spontaneous and ART twins according to gender.